Lemma LSP

Language Server Protocol implementation for Lemma. Provides inline diagnostics and editor features for .lemma files.

Features

• Diagnostics — Parse and planning (semantic) errors are published as you type. Parse errors are shown immediately; a debounced (250ms) full workspace validation adds planning errors. Errors use source spans where available; diagnostics are cleared when a file is closed.
• Workspace validation — On native, when the client provides a workspace root, the server scans for .lemma files under that root at startup (skips hidden directories only) and runs full planning so cross-spec errors (missing spec/type refs, circular dependencies, etc.) are reported per file. The client keeps the server in sync via file open/change/close. On WASM, only the open file is validated (no filesystem).
• Registry links — @-prefixed Registry references (e.g. spec @user/workspace/somespec, type ... from @iso/countries/alpha2) are turned into clickable links when the Registry (LemmaBase) provides a URL. Works even when the file has parse errors (text-based scan).
• Registry hover — Hovering on a registry uses reference (qualifier or spec name) shows a popup with exactly two navigation entries: a hover-markdown link to the LemmaBase page for the repository, and the DocumentLink Ctrl+Click hint to the locally fetched bundle under <workspace>/lemma_deps/<qualifier>.lemma at the resolved spec ... line.
• Embedded stdlib navigation — uses lemma units (and any other reserved repo lemma import) becomes a clickable link to a view-only snapshot at <workspace>/lemma_deps/lemma.std. The file is written lazily the first time document_link runs on a spec that imports it, and is excluded from every .lemma discovery pass because of its .std extension. The repository qualifier link opens the file; the spec name link opens it at the spec ... line. The VS Code extension registers the lemma.std filename so the snapshot still gets full Lemma syntax highlighting.
• Text document sync — Full file sync on open, change, and close; no incremental sync.

The server uses the Lemma engine with registry support (LemmaBase) for resolving @... identifiers and communicates over stdio (native) or browser streams (WASM).

Build

From the repository root:

cargo build --release -p lemma

The LSP runs as lemma lsp (stdio).

The crate also supports a WASM build for in-browser use; the library entry point is lsp::browser::serve. The Lemma WASM playground does not use the LSP for diagnostics; it uses the engine’s getDiagnostics API directly for inline errors.

Usage

Run the server over stdio:

lemma lsp

• VS Code / Cursor — Use the extension under editors/vscode. It runs lemma lsp automatically and looks for target/release/lemma when the workspace root is the Lemma repo, or uses the lemma.lspServerPath setting. Format-on-save and diagnostics only work when the LSP is running; see editors/vscode/README.md if format on save does nothing.
• Other editors — Point your editor’s LSP client at lemma with argument lsp and stdio transport.

Layout

• src/ — LSP server (tower-lsp): server, diagnostics, registry links, workspace model, registry integration.
• editors/ — Editor-specific clients and config (e.g. VS Code extension); see editors/README.md.